Biomechanics, Volume 3, Issue 4 (December 2023) – 13 articles

This study aims to investigate the effect of ridged (micro-grooved) surface finish over the trunnion surface on the mechanics (stress, strain, and deformation) of the head–neck taper interface in hip implants. Using finite element modelling, the study focused on the geometric parameters of such micro-grooves to study how they would mechanically affect stress and deformation fields after the assembly procedure. As such, five different 2D models with varying micro-groove height and spacing were produced and assembled under an impaction assembly force of 4 kN in a 32 mm CoCrMo head engaged with a 12/14 Ti-6Al-4V neck. The results showed that lower von Mises stresses could be induced by either an increase or decrease in spacing against the base model (Model 1), which probably signifies that the relationship between the ridge spacing and stress may depend on the level of spacing. It was concluded that the geometrical parameters of the ridges (and their non-linear interactions) impact not only the stress and strain fields but also the assembly loading time at which the maximal stress and plastic deformation occur. Full article

We investigated the influence of Achilles tendon (AT) geometry on local-strain magnitude and distribution during loading, using finite element analysis. We calculated the following eight AT parameters for 18 healthy men: thickness and width of the most distal part, minimum cross-sectional area (mCSA), and most proximal part; length; and position of the mCSA. To investigate the effect of AT geometry on the magnitude and distribution of local strain, we created three-dimensional numerical models by changing the AT parameter values for every one standard deviation (SD) in the range of ±2 SD. A 4000 N lengthening force was applied to the proximal surface of all the models. The mean first principal strain (FPS) was determined every 3% of the length. The highest FPS in each model was mainly observed in the proximal regions; the 86–89% site (the most proximal site was set at 100%) had the highest number of models with the highest FPS (nine models). The highest FPS was observed in the model with a distal thickness of −2 SD, which was 27.1% higher than that of the standard model observed in the 2–5% site. Therefore, the AT geometry influences local-strain magnitude and distribution during loading. Full article

Background: Children’s gait is traditionally understood to mature as young as three years old through pre-adolescence. Studies looking at gait biomechanics suggest that gait matures around three years old, while studies investigating gait variability propose a much later maturation. The studies that have examined children’s gait variability did so while the children walked around a track or down hallways that created a discontinuous gait, potentially affecting the measures of variability and the efficacy of the results. Purpose: Therefore, the purpose of our study was to investigate the development of gait dynamics and gait variability in children in a more continuous fashion, in this case, by walking on a treadmill. Methods: To accomplish this, we included four age groups of children, ranging 2–10 years old, walking on a treadmill for at least three minutes while stride time and stride length were collected. Stride time and stride length’s variability was then analyzed using linear (mean, standard deviation, coefficient of variation) and nonlinear (sample entropy, detrended fluctuation analysis) measures across the varying ages of our participants. Results: Interestingly, both the linear and nonlinear variabilities of the stride time and stride length measures decreased as the groups of children got older. Specifically, CV ST (2–3 (9.3 ± 4%), 8–10 (3.6 ± 0.7%), p < 0.05) and CV SL (2–3 (11.4 ± 3%), 8–10 (4.6 ± 1%), p < 0.05) were our strongest linear measures, and DFA α ST (2–3 (0.97 ± 0.12), 8–10 (0.82 ± 0.10), p < 0.05) and DFA α SL (2–3 (0.91 ± 0.04), 8–10 (0.81 ± 0.03), p < 0.05) were our strongest nonlinear measures, particularly between the youngest and oldest groups. This trend of variability decreasing with age suggests that as children’s gait matures, their gait becomes more stable and reliable. Significance: Our study rejects the notion that children’s gait is mature by the age of three, as some would suggest. By analyzing the variability of stride time and stride length, we can see that even later into childhood, children’s gait continues to change and evolve. Full article

Background: Agreement between the activities-specific balance confidence scale (ABC) and center of pressure (CoP) in prosthesis users is still very much unknown. The purpose of this study was to investigate the agreement between ABC and CoP in lower-limb prosthesis users. Methods: Twenty-one individuals with lower-limb prostheses were recruited. Participants were provided with the ABC scale and performed static balance tasks during eyes opened (EO) and eyes closed (EC) conditions whilst standing on a force platform. Pearson product moment coefficients between CoP displacements and ABC scores were performed. Participants were also stratified by those who had better (≥80 on ABC scale) and less (<80 on ABC scale) perceived balance confidence. Displacement was compared using an independent t-test with Cohen’s d to estimate effect size with alpha set at 0.05 for these tests. Results: There was a significant inverse moderate relationship between eyes opened displacement (EOD) (18.3 ± 12.5 cm) and ABC (75.1 ± 18.3%), r = ₍₁₉₎−0.58, p = 0.006, as well as eyes closed displacement (ECD) (37.7 ± 22.1 cm) and ABC, r = ₍₁₉₎−0.56, p = 0.008. No significant difference in EOD (t₍₁₉₎ = 1.36, p = 0.189, d = 0.61) and ECD (t₍₁₉₎ = 1.47, p = 0.156, d = 0.66) was seen between those with greater and less balance confidence. Conclusions: Self-report and performance-based balance outcome measures are recommended when assessing lower-limb prostheses users. Full article

This study validated muscle activation estimations generated by OpenSim during the gait of elderly fallers. Ten healthy elderly participants walked on an instrumented treadmill, monitored by motion capture, force platforms, and 12 surface EMG sensors. Static optimization was used to calculate muscle activations, evaluated through cosine similarity, comparing them with EMG signals from 12 muscles of the right leg. Findings revealed varied similarity levels across muscles and gait phases. During stance phase, tibialis anterior (TIBA), peroneus longus (PERL), soleus (SOL), gastrocnemius lateralis (GASL), semitendinosus (SEMI), tensor fasciae latae (TFL), and rectus femoris (RECF) demonstrated poor similarity (cosim < 0.6), while gluteus medius (GMED), biceps femoris long head (BFLH), and vastus lateralis (VL) exhibited moderate similarity (0.6 ≤ cosim ≤ 0.8), and gluteus maximus (GMAX) and vastus medialis (VASM) displayed high similarity (cosim > 0.8). During the swing phase, only SOL demonstrated inadequate similarity, while GASL, GMAX, GMED, BFLH, SEMI, TFL, RECF, and VASL exhibited moderate similarity, and TIBA, PERL, and VASM showed high similarity. Comparing the different 10% intervals of the gait cycle generally produced more favorable similarity results. For most of the muscles and intervals, good agreement was found. Moderate agreement was estimated in the cases of TIBA (0–10%), PERL (60–70%), GASL (60–70%), TFL (10–20%), RECF (0–10%, 80–100%), and GMED (50–60%). Bad agreement was found in the cases of SOL (60–70%), GASL (0–10%), and TFL (0–10%). In conclusion, the study’s validation outcomes were acceptable in most cases, underlining the potential for user-friendly musculoskeletal modeling routines to study muscle output during elderly gait. Full article

Background: Taking inspiration from the classical 1974, “moving room experiment” by Lee and Aronson, a “virtual moving room paradigm (Vroom)” was designed using virtual reality (VR) to assess postural control behavior. Methods: Thirty healthy adults (age: 21 ± 1 years; height: 166.5 ± 7.3 cm; mass: 71.7 ± 16.2 kg) were tested for postural stability in a virtual moving room paradigm (Vroom). The Vroom consisted of randomized virtual and visual perturbations of the virtual room moving toward and away from the individual, during both unexpected and expected trials. Objective postural sway variables and subjective experiences to VR using the simulator sickness questionnaire as well as balance confidence scale were also assessed and analyzed using a two way (2 × 2 [2 moving room direction (Toward vs. Away) and 2 knowledge of moving room (unexpected vs. expected)] repeated measures analysis of variance (ANOVA), and a one-way repeated measures ANOVA and paired sample t-test, respectively at an alpha level of 0.05. Results: Significantly greater postural sway was observed when the virtual room moved toward the participant than when moving away, and when it moved unexpectedly, compared with the expected moving room. Significantly improved balance confidence with realistic immersion and without simulator sickness was also observed. Conclusions: Our findings provide evidence indicating that the virtual moving room induces postural perturbations that challenge the postural control system, especially when the moving room is unexpected and moves toward the individual. Additionally, increased balance confidence and realistic immersion in the virtual environment with no adverse effects of simulator sickness were observed, providing evidence for the beneficial effects of the Vroom. Thus, the Vroom can be an easy and cost-effective method to expose individuals to realistic, virtual, and visual perturbations that challenge the postural control system and increase balance confidence, with realistic immersion and without adverse effects. Full article

Forefoot osteotomies to improve the alignment are difficult procedures and can lead to a variety of complications. Preoperative planning in three dimensions might assist in the successful management of forefoot deformities. The purpose of this study was to develop a global coordinate system in the foot for the planning of forefoot corrections. Two strategies (CS1 and CS2) were developed for defining a global coordinate system that meets the criteria of being well-defined, robust, highly repeatable, clinically relevant, compatible with foot CT scans, independent of the ankle joint angle, and does not include bones in the forefoot. The absolute angle of rotation was used to quantify repeatability. The anatomical planes of the coordinate systems were visually inspected by an orthopedic surgeon to evaluate the clinical relevancy. The repeatability of CS1 ranged from 0.48° to 5.86°. The definition of CS2 was fully automated and, therefore, had a perfect repeatability (0°). Clinically relevant anatomical planes were observed with CS2. In conclusion, this study presents an automated method for defining a global coordinate system in the foot according to predefined requirements for the planning of forefoot corrections. Full article

Sacroiliac (SI) joint dysfunction can lead to debilitating pain but can be treated with minimally invasive sacroiliac joint fusion (SIJF). This treatment is commonly performed using 2D fluoroscopic guidance. This makes placing the implants without damaging surrounding neural structures challenging. Virtual surgical planning (VSP) using simulated fluoroscopic images may improve intraoperative guidance. This article describes a workflow with VSP in SIJF using simulated fluoroscopic images and evaluates achieved implant placement accuracy. Ten interventions were performed on 10 patients by the same surgeon, resulting in a total of 30 implants; the median age was 39 years, and all patients were female. The overall mean implant placement accuracy was 4.9 ± 1.26 mm and 4.0 ± 1.44°. There were no malpositioning complications. VSP helped the surgeon understand the anatomy and determine the optimal position and length of the implants. The planned positions of the implants could be reproduced in surgery with what appears to be a clinically acceptable level of accuracy. Full article

Approximately 82% of amputees prefer microprocessor knees (MPKs) to the passive alternatives. However, the cost of these devices makes them inaccessible for many patients. The aim of this research is to develop an affordable MPK that allows for stumble reduction and flexion dampening at a fraction of the cost of similar devices. The GKnee was developed by a sophisticated mathematical model that can effectively calculate geometric configuration and simulate forces transferred through a prosthetic knee at any given point through the gait cycle. With a median error of 6%, the mathematical model was developed to the point of reasonable accuracy for determining component placement and force interactions. The model served as a valuable tool to assist in the iterative design process of the GKnee, influencing component selection for the hydraulic system and frame design. This model was then validated using a compression rig and a mock GKnee prototype. The GKnee was then evaluated for its ability to perform under expected loading conditions, using compression testing and dynamic flexion testing. This research led to the development of a sub USD 500 microprocessor prosthetic, while remaining under 2.27 kg. Full article

Biomechanical analysis has been one of the most used procedures when aiming to improve performance in sports and is also very relevant and decisive in the final classification of competitive events in sports such as gymnastics. Hence, this study sought to provide an overview of the number of scientific literature publications related to biomechanics research in gymnastics. The document search was completed in March 2023 and reflected a bibliometric analysis considering the published manuscripts up to 31 December 2022. Data collection was performed on the Web of Science, following the bibliometric analysis law, using Microsoft Excel and VosViewer Software (v1.6.19) for analysis and data processing. A total of 325 documents related to the topic under study were located. The results highlight that the older manuscripts date from 1980, with a growing trend of publications from that moment until now and a very visible increase in 2015, and that Sport Science is the category associated with more published manuscripts. A total of 30 manuscripts have 30 or more citations, 746 authors and co-authors are associated with the publications, and 58 co-authorships have published one or more studies. Moreover, 47 countries or regions have been associated with the topic under study, with the USA, England, and Australia being the countries with the most published articles and citations. The study also found that the highest frequency keywords are: “gymnastics” (n = 122), “biomechanics” (n = 73), “simulation” (n = 27), and “performance” (n = 25), considering the average year of publication of the documents, “balance” (n = 11), “artistic gymnastic” (n = 14) and “training” (n = 25) are the most frequently used terms. This study reveals that the topic of biomechanics in gymnastics has shown sustained growth and deserves the attention of the scientific community, but at the same time, there is still much room for research development. Full article

This study aimed to report the shooting velocities and to assess the differences in shot velocity according to the techniques used in elite youth male rink hockey players. Fifteen rink hockey players (age = 18.40 ± 1.44 year; body mass = 73.52 ± 6.02 kg; height = 1.76 ± 0.06 m; BMI = 23.61 ± 2.12; sports experience = 6.44 ± 1.76 years) participated in this cross-sectional study. Shooting velocities were assessed for four techniques: slap shot without approach run, drive shot without approach run, slap shot with approach run, and drive shot with approach run. Shooting velocity measurements were conducted using a radar Stalker ATS systemTM. The results demonstrated that drive shots consistently achieved higher velocities compared to slap shots (F(_3,56) = 23.9 p < 0.01, η_p² = 0.58). Additionally, incorporating an approach run significantly increased shooting velocities for both techniques (p < 0.01). These findings hold significant implications for coaches and players seeking to optimize shooting performance in rink hockey. Full article

An increased jumping performance is key for gymnastics competition routines. Rhythmic gymnasts (RGs) use the jump as one of the main body elements. In Acrobatic Gymnastics (ACRO), top gymnasts must coordinate their jumps with the impulse provided by base gymnast(s). It is expected that the gymnasts’ discipline and role played impact their jumping skill. This work aims to investigate how the jumping performance differs between ACRO gymnasts and RGs, focusing on the Force–Velocity (F-V) profile mechanical variables. Gymnasts were divided in three groups: ACRO tops (n = 10, 13.89 (3.62) median (interquartile interval) years old), ACRO bases (n = 18, 18.24 (4.41) years old) and RGs (n = 15, 12.00 (3.00) years old). The F-V profile during countermovement jump and its mechanical variables were evaluated using MyJump2. A training background survey and anthropometric assessments were conducted. The significance level was set at p ≤ 0.05. Group comparisons showed that ACRO bases jump higher than ACRO tops and RGs, present a higher maximal force than RGs and a more balanced F-V profile, while RGs present high force deficits. Coaches can use this data to develop interventions that optimize the training stimulus to different gymnastics disciplines considering the individual characteristics and adaptability of each gymnast. Full article

Cervical disc degenerative disease (CDDD) is a common spinal pathology that is often treated with anterior cervical discectomy and fusion (ACDF), cervical disc arthroplasty (CDA), and/or hybrid cervical surgery (HCS). The purpose of this first-time systematic review is to examine the biomechanical outcomes associated with three types of non-contiguous cervical surgeries—ACDF, CDA, and HCS—to provide a greater understanding of non-contiguous cervical surgical biomechanics. A systematic review was performed using PubMed, Cumulated Index to Nursing and Allied Health Literature (CINAHL), MEDLINE, and Web of Science from database inception until June 6th, 2023. The inclusion criteria was any article that reported biomechanical or kinematic outcomes, outcomes for any of the three non-contiguous cervical surgeries, and human-derived and/or human cadaver subjects. A total of 5 biomechanical articles were included from a total of 523 articles. Non-contiguous two-level HCS experienced less drastic range-of-motion (ROM) changes throughout the cervical spine and decreased intervertebral disc pressure (IDP) compared to non-contiguous two-level ACDF. Non-contiguous two-level CDA resulted in more cervical ROM and less non-operative segment facet contact force compared to non-contiguous two level ACDF. There was less cephalad and caudal non-operative segment ROM in non-contiguous two-level ACDF compared to contiguous three-level ACDF. Full article